This invention generally relates to the field of wiping blades. Particularly it relates to the field of drag shoes for street sweepers, by which is meant street cleaning machinery utilizing debris-removal techniques including but not limited to rotating brushes, vacuum, and regenerative air systems, respectively. Nevertheless, for definitiveness, the following discussion will be directed to street sweepers utilizing the brush mechanism.
Street sweepers generally comprise a tractor-like vehicle, rotating brushes, a means to transport swept-up debris from the street and a hopper into which the debris is tranported. One of the major functions of the rotating brushes is to sweep road debris forward, up off of the road surface and onto or into the transporation/removal system. If the outside ends of this forward sweeping brush are not contained at road level, a significant amount of the road debris can escape laterally. Therefore, drag shoes are used to contain such debris. Drag shoes are positioned such that their length dimension is parallel to the axis of travel of the sweeper machine and therefore perpendicular to the sweeper brush. Also their height is much greater than their width. As their name suggests, these shoes then drag on the road surface, and in this manner, they keep the road debris from escaping laterally from the sweeper brush.
Traditionally, these drag shoes have been made in a number of ways. First, drage shoes of a soft rubber have been used. These have required the use of metal stiffeners to give the shoes the necessary longitudinal stiffness. However, if these drag shoes are deformed by contact with, e.g., curbs, grates, or railroad tracks, the deformations are made permanent by the concurrent deformation of the metal stiffener. Also, the use of soft rubber results in a short life span for the drag shoe as the rubber is quickly abraded by contact with the road surface. Second, drag shoes of steel have been used. In many cases, these drag shoes have included a hard, wear-resistant material e.g., U.S. Pat. No. 4,450,601 to Schwayder. Again, deformations of these drag shoes are permanent due to the use of at least one strip of metal along the length of the shoe. Also, the use of steel along the bottom of the shoe results in the creation of sparks as the shoe is dragged along the road surface.
Therefore, what is needed is a drag shoe which is resilient, which will not be subject to permanent deformations, which is stiff enough so it does no need any metal or non-resilient stiffeners, and which is sufficiently abrasion-resistant to provide for a long working life.